1. Field of the Invention
The present invention generally relates to a mechanism for an optical disc driver, and more particularly to a tilt angle adjusting mechanism for adjusting the tilt angle of an optical axis of the pickup head relative to the optical disc.
2. Related Art
The drivers for optical disc become more and more popular, and even indispensable in the current information industry. For example, drivers for reading CD ROM or DVD ROM has now been well matured.
The spindle motor in an optical disc driver has to be precisely positioned in order to keep the data bearing surface of the optical disc, e.g., CD or DVD, perpendicular to the optical axis of the objective lens in the optical pickup head, so that the information data can be correctly read. Generally, the tilt angle of a spindle motor (which rotates the optical disc) relative to the optical pickup head or the guide rods (which support the pickup head) has to be well adjusted to the right position. The conventional tilt angle adjusting mechanisms can be classified into two kinds:
1) by adjusting the spindle motor. In this manner, the adjusting mechanism which piles on the spindle motor will occupy a certain space, easily pierce holes on the circuit board mounted adjacent to it, increase the complexity of mechanical design, increase the difficulty of adjustment, and restrain a compact design of optical disc driver;
2) by adjusting the guide rods. This manner will cause the transmission mechanism of the optical pickup head fail when the pickup head is driven via a gear-tack transmission.
Please refer to FIG. 1 which is a partial exploded view of a conventional optical disc driver. The optical disc driver mainly includes a spindle motor 40, an optical pickup head 10 and a sheet metal base 20. The spindle motor 40 is fixed on a motor base 43 which is further fixed to the well planed sheet metal base 20. An objective lens 11 is positioned on the optical pickup head 10 which is movably mounted on two guide rods 30a and 30b. The guide rods 30a, 30b support two ends of optical pickup head 10 in which one end is furnished with a round hole 100 and the other end is a square slot 101. Ends of the guide rods 30a, 30b are fixed to the sheet metal base 20 via mounts 21a, 21b, 21c and 21d. The paralleling and positioning of the guide rods 340a, 30b are determined by the precision and positioning of the mounts 21a, 21b, 21c, 21d and the sheet metal base 20.
The motor base 43 of the spindle motor 40 is fixed with one point to the sheet metal base 20 via a stud 44 and a fixing screw 45, and with other two points movably linked to the sheet metal base 20 via adjusting screws 46a, 46b which will change the distance and tilt angle of the motor base 43 relatively to the sheet metal base 20 so as to adjust the tilt angle of the spindle motor 40 relatively to the optical pickup head 10 for correctly reading data from an unshown optical disc. But, the aforesaid adjusting mechanism causes problems of occupying an extra space adding to the spindle motor 40, and the screws 45, 46a, 46b may pierce holes on a circuit board mounted adjacent to the spindle motor 40.
The present invention mainly provides a tilt angle adjusting mechanism for adjusting a tilt angle of an optical axis of a pickup head relative to the optical disc so that the data stored on the optical disc can be correctly read by a laser beam coming from and returning to the pickup head.
Another object of the present invention is to provide an adaptive mechanism for adjusting the tilt angle of a pickup head without modifying the original structure of the optical disc driver.
The tilt angle adjusting mechanism according to the present invention, for adjusting the optical axis of the pickup head perpendicular to the plane of the optical disc, includes:
a first and a second guide rods, parallel to each other and located in a X-Y plane where the rods extend in the Y axis, for carrying the optical pickup head;
an optical pickup head, contacting the first guide rod at a first and a second points along the Y-axis, and contacting the second guide rod at a third point;
a first and a second adjusting elements normally contact respectively at the first and the second points to the first guide rod;
a third adjusting element normally contact at the third point to the second guide rod;
the first and the second adjusting elements are movable for adjusting the pickup head rotating on the X-axis; and the third adjusting element is movable for adjusting the pickup head rotating on the Y-axis.
The three contacting points can be designed with some suitable shapes, such as long round holes, square holes, L-shape base or square slots, and incorporated with pressing elements which provide pre-loadings to the guide rods, for contacting the guide rods with the adjusting elements. The adjusting element can be a stud with a round end, or a screw pushing a steel ball, for a point contact to the guide rod in order to attain the tilt angle adjustment. An adaptive mechanism can also be provided for adjusting the tilt angle of a pickup head without modifying the original structure of an optical disc driver.